With the development of communication systems, a variety of information is shared and e-commerce, banking and certificate issuance such as a copy of the resident registration have been widely implemented in wire/wireless data communication environments. If a user terminal (client) such as a personal computer accesses an on-line market managing server, then a banking server or a public office server (hereinafter referred to as a service providing server) through open network such as Internet, data transmission/reception between the user terminal and the service providing server may be implemented. The user terminal and the service providing server may encode the data by using a secure sockets layer (SSL) to transmit and receive the data. This is so that information leakage may be prevented in advance from potential hacking.
However, the conventional SSL have a limitation in that a certificate should be installed on the service providing server. Further, additional ports have to be assigned so as to install a plurality of certificates on one service providing server, which increases the server capacity. Thus, it is not easy to manage the server from the perspectives of web-hosting providers or application server providers.